A method whereby audio data recorded on a compact disc (CD) is compressed by an MP3 (MPEG1 Audio Layer-3) system and the compression data is transmitted and received via a network is widely used. Thus, a process to secure contents (specifically speaking, encryption of the contents) is necessary from a viewpoint of protection of a copyright of music contents. Such compression of the audio data or the process to secure the music contents is usually executed on the basis of an error correcting method in a similar format to the existing format.
In the case where the contents has a linear PCM signal format, usually, errors which could not be corrected by an added error correction code are processed so as to be inconspicuous on a reproduction signal by an interpolating process such as mean Value interpolation or the like. However, in a compression encoding process, for example, a DCT (Discrete Cosine Transform) process is executed on a block unit basis. There are problems such that in the case where data obtained after the DCT process has errors, it is difficult to interpolate the erroneous data by an interpolating technique similar to that in the case of the linear PCM signal, and when the compressed data is decompressed and converted into an audible sound, an influence of the errors is likely to be offensive to the ear.
In the case of contents with a high added value which is charged for when contents data is downloaded via the network or is charged for when the contents data is read out from a medium and reproduced, sufficient reliability is not obtained by error correcting ability equivalent to that of the existing error correction code. For example, in the case where the data obtained by compressing contents data with a high added value by the MP3 system is recorded onto a disk as a recording medium on the basis of a format (that is, mode 1 or mode 2 (form 1)) with an error correcting function of a CD-ROM, although correcting ability for random errors is improved more than in the case of error correcting ability of a CD-DA (Digital Audio) format, correcting ability for burst errors which are caused due to a scratch on the disc, dust on the disc, or the like is not improved more than in the case of the CD-DA format. This means that the reliability of contents which is charged for or contents whose copy limitation is severe is equivalent to that of contents which are free or in which copy restriction is mild or there is no copy limitation, so that the user is unsatisfied.
It is, therefore, an object of the invention to provide a recording method and a recording apparatus of a recording medium and a reproducing method and a reproducing apparatus of the recording medium, in which error correcting encoding can be switched in accordance with data to be recorded.